Employing The Carbon Film To Improve The Impact Wear Resistance Of Micro-punching Needle For Spinning

The surface coating method is used to deposit a film with high hardness and strong film-substrate cohesion on the surface of the micro-punching needle for spinning,which is expected to alleviate the impact and wear of the micro-punching needle in the working environment for a long time.Unfortunately,the tip effect of tools,who have an irregular micro-scale surface,in coating external field prevents the deposition of film on the tool surface successfully.This study investigated the mechanism of the tip effect in the diamond-coating environment where the process conditions and film formation mechanism have been thoroughly studied,a two-step method is used to deposit a diamond film on the surface of the needle.During this period,we study the tip effect of the micro-needle in the electric field and temperature field.The purpose of this approach was to reveal the mechanism of the tip effect;deposit Cr-doped diamond-like film on the surface of the micro-punching needle to explore the relationship between the metal doping amount,the film hardness,the film-substrate cohesion,and the impact wear resistance of the needle;change the substrate roughness of the needle,to explore the relationship between the substrate roughness,the film-substrate cohesion,and the impact wear resistance of the needle.Finally,we obtain the best performance parameters which is suitable for the impact wear environment of the needle.The main conclusions are:(1)The tip effect of the micro-needle in the coated external field is related to its internal electronic rearrangement.The free electrons in the micro-needle will absorb the energy in the external field to overcome the strong interaction force of the nucleus,and preferentially move to the tip after being free.Resulting in a higher concentration at the tip and the tip effect.(2)The doping amount of Cr affects the impact wear resistance of the needle by adjusting the phase composition of the film and the relative content of different types of carbon bonds.Cr reacts with the carbon in the film to produce metal carbides,consuming part of the sp~3-C bonds,and changing the relative content of sp~2 and sp~3carbon bonds in the film,which in turn brings a series of changes in the mechanical properties of the film.As a result,the DLC film with Cr content of 11.08 improved the impact resistance of the needle the most.(3)The roughness of substrate affects the impact wear resistance of the needle by changing the contact interface between the substrate and the film.The internal stress of the film,the mechanical locking force of the interface,and the interfacial gap will change with the substrate roughness.When the substrate roughness is 72.94 nm,the film-substrate cohesion reaches the maximum 72.24 N.At this time,the film has the best modification effect on the needle.